Incinerators of this kind already existing utilize a rotary furnace coated internally with refractory material. One drawback of these furnaces is that the refractory coating is subject to damage caused by hard objects and explosive material such as metal and spray cans. It follows that they require frequent repairs by highly-qualified personnel, which repairs are time-consuming and consequently very costly.
A further drawback of these rotary furnaces is their considerable weight and very large size, both factors which make it impossible to install these incinerators on motor vehicles of reasonable proportions. Furthermore, rotary furnaces coated with refractory material are subject to a high degree of thermal inertia. Consequently, it takes a long time for them to reach their operating temperature and an equally long time to cool off, with the result that any repair necessitates excessively long stoppages.
Still other existing incinerators make use of rotary furnaces which have no refractory coating. These do have a lower weight and smaller size, as well as less thermal inertia, than furnaces coated with refractory material; however, they suffer from high wear since the interior walls are directly in contact with the burning waste. It follows that their useful life is relatively short. Furthermore, these furnaces are mostly of a tubular shape and must be very long since the waste must move at the same slow speed both in dessication stage and in the actual incineration stage. They cannot burn liquid wastes since these would leak out.
It is an object of this invention to provide an incinerator having a lightweight rotary furnace small enough so that the incincerator can be mounted on a normal tuck.
A further object of this invention is to provide an incinerator having a rotary furnace whose outer walls are forcibly cooled, which consequently has a longer life-span, and in which it is possible to burn liquid waste as well without having it leak out.
It is still another object of this invention to provide an incinerator having an easily manufactured rotary furnace which can be installed and removed as well as replaced directly on site by non-specialized personnel since, because of its low thermal inertia, long stoppages are avoided.
Yet another object of this invention relates to the provision of an incinerator discharging only such combustion gases as are vertually free of solids, completely burned and sterile and thus do not pollute the environment, thus enabling operation of the incinerator in residential areas, for example as a mobile unit which collects refuse directly from homes and disposes of it right on the spot.
These objects can be achieved, according to this invention, in that the furnace further comprises first and second cylindrical sections connected by a hollow, frustoconical connecting piece which is shorter than both the first and second sections, the first section containing the drying chamber and the second section containing the incinerating chamber, the first section being shorter in length and larger in diameter than the second section so that the drying chamber is shorter in length and has a larger inside diameter than the incinerating chamber and has a laterally closed-off portion; a refuse entry gate disposed at the end of the first section remote from the section and having an inside diameter smaller than that of the first section, the laterally closed-off portion of the drying chamber being situated below the level of the entry gate and the incinerating chamber for preventing liquid refuse from flowing out of the drying chamber; a slag and cinder outlet opening disposed at the end of the second section remote from the first section; a screw conveyor disposed on that portion of the inside wall of the drying chamber nearest the entry gate; a first series of conveyor blades disposed on the remainder of said inside wall of said drying chamber; a second series of conveyor blades disposed on the inside wall of the connecting piece; a third series of conveyor blades disposed on the inside wall of the incinerating chamber from the junction thereof with the connecting piece to the vicinity of the outlet opening; and a fourth series of conveyor blades disposed immediately adjacent to the outlet opening, the blades of the first series having an angle of pitch, relative to the axis of rotation, which is greater than that of the third series but less than that of the second and fourth series, and the blades of the second series having an angle of pitch, relative to the axis of rotation, which is less than that of the fourth series, the refuse thereby being rapidly carried away from the region of the entry gate by the screw conveyor upon rotation of the furnace, then moved relatively slowly through the drying chamber by the first series of blades for the purpose of drying and preheating, thereafter transported relatively quickly through the connecting piece into the incinerating chamber by the second series of blades, and moved on by the third series of blades within the incinerating chamber more slowly than in the drying chamber for being incinerated until the resultant ash reaches the fourth series of blades and is rapidly removed thereby from the rotary furnace through the outlet opening; and the incinerator further comprising for cooling the outer wall of the furnace: a stationary cooling chamber in which the furnace is mounted for rotation, at least one pusher fan for supplying cooling air to the cooling chamber, adjustable air-flow control means disposed between the at least one pusher fan and the cooling chamber for adjusting the rate of flow of the cooling air through the cooling chamber, and air-flow chanelling screens disposed on each side of the upper half of the rotary furnace and spaced therefrom for directing the cooling air around the upper half of the furnace, the screens defining an elongated opening above the furnace for the escape of the cooling air from the cooling chamber.